THIS PROPOSAL CONCERNS THE INTERFACE BETWEEN PHOTONICS AND MICROWAVES, A DYNAMIC AREA OF RESEARCH NOW MATURED TO A POINT WHERE MAJOR APPLICATIONS ARE FEASIBLE. THE OBJECTIVE IS THE DEVELOPMENT OF MONOLITHIC INTEGRATED PHOTONIC-MICROWAVE DEVICES, WHICH WOULD GREATLY ENHANCE THE PERFORMANCE OF HIGH-SPEED FIBEROPTIC LINKS. FOR MICROWAVE APPLICATIONS, THERE IS AN INTEREST IN TRANSMITTING OPTICAL SIGNALS TO AND FROM MMIC CHIPS. THUS, OPTICAL INPUT AND OUTPUT PORTS FOR MONOLITHIC MICROWAVE INTEGRATED CIRCUITS (MMIC) WILL BE DEVELOPED. WE WILL INVESTIGATE THE USE OF MESFETS AND HEMTS, THE BASIC BUILDING BLOCKS OF MMICS, AS OPTICAL INPUT PORTS ON THESE CHIPS. USING FREE CARRIER INJECTION/DEPLETION AS THE BASIC INTERACTION MECHANISM, WE WILL ALSO STUDY THE DEVELOPMENT OF EXTERNAL MODULATORS ON MMICS AS OUTPUT PORTS. THE USE OF THIS MECHANISM INSTEAD OF THE ELECTROOPTICAL EFFECT PROVIDES A UNIQUE OPPORTUNITY TO MAKE HYBRID DEVICES VIA WELL DEVELOPED, RELIABLE, AND COST EFFECTIVE SEMICONDUCTOR PROCESSING AND FABRICATING METHODS. DEVICE INTERACTION WILL BE STUDIED TO DETERMINE THE EFFECTIVENESS OF THE EXTERNAL MODULATOR IN TERMS OF DYNAMIC RANGE, NOISE CHARACTERISTICS, AND OPERATING CONDITIONS. EMPHASIS WILL BE ON COMPATABILITY WITH MMIC PROCESSING AND ON INNOVATIVE PACKAGING. PHASE I WILL STRESS ANALYTIC AND SIMULATION STUDIES THROUGH WHICH THE MOST PROMISING DEVICE CONFIGURATIONS WILL BE IDENTIFIED FOR EXPERIMENTAL IMPLEMENTATION UNDER PHASE II.